1. Field of the Invention
The present invention relates generally to an image forming apparatus. More particularly, the invention relates to an image forming apparatus having a squeezing roller for applying a pressure in order to remove a solvent in a liquid toner from an image developed on a photoconductive drum which is formed with a photoconductor on a surface thereof.
2. Description of the Related Art
Conventionally, as shown in FIG. 5, in an image forming apparatus having a squeezing roller 17 for removing a solvent in a liquid toner from an image developed on a photoconductor belt 15, it has been known that a load distribution in a roller axis direction between a squeezing roller 17 and a back-up roller 18 is required to achieve a uniform drying ratio over the entire image. For this purpose, a surface elastic body of the squeezing roller 17 is formed into a crown shape.
However, in the conventional image forming apparatus constructed as set forth above, in order to clean toner particles which are mechanically or electrically deposited on the squeezing roller 17, a cleaning roller 16 that electrically removes the toner particles on the squeezing roller 17 is provided at an opposite position to the contacting surface of the photoconductor belt 15. Since the surface elastic body of the squeezing roller 17 is formed into a crown shape, field gap in the axial direction of the squeezing roller tends to be non-uniform.
In the conventional image forming apparatus, the tip end portion of a cleaning blade (not shown) is positioned so a to clean the toner particles electrically deposited on the cylindrical outer periphery of the cleaning roller 16. The cleaning blade contacts stirring hair of a brush roller (not shown) so as to remove toner particles firmly stacked on the tip end portion thereof. The tip end position of the cleaning blade becomes significantly worn due to the rubbing of the tip end portion of the cleaning blade by the brush roller.
The present invention in the conventional image forming apparatus as set forth above. Therefore, it is an object of the present invention to provide an image forming apparatus which compensates for the unevenness of the field gap in an axial direction of a squeezing roller, can efficiently clean the squeezing roller, and can prevent the wearing of a tip end portion of a cleaning blade due to rubbing so as to provide a longer life.
In order to accomplish the above-mentioned and other objects, an image forming apparatus, in accordance with one aspect of the present invention, comprises:
a solvent-based liquid toner;
a squeezing roller applying a predetermined pressure on the liquid toner on a photoconductor belt for removing the solvent in the liquid toner from an image developed on the photoconductor belt;
a cleaning roller arranged at a position opposing to the squeezing roller for removing a toner particle depositing on a cylindrical outer peripheral surface of the squeezing roller by application of a voltage; and
a spacer maintaining a given clearance between a cylindrical outer peripheral surface of the squeezing roller and a cylindrical outer peripheral surface of the cleaning roller.
With the invention set forth above, since the clearance between the cylindrical outer peripheral surface of the squeezing roller and the cylindrical outer peripheral surface of the cleaning roller is maintained, at a set distance by the spacer a field gap in the axial direction of the squeezing roller will not become uneven, and therefore, permit efficient cleaning of the squeezing roller.
In the preferred construction, the squeezing roller may include a cylindrical bare pipe; an elastic body attached on a cylindrical outer peripheral surface of the bare pipe; and a shaft extending through the bare pipe. The bare pipe and the shaft are preferably connected at two points along a substantially central portion along the axial direction of the squeezing roller.
In the preferred construction, the pressure between the photoconductor belt and the squeezing roller in the axial direction of the squeezing roller can be made uniform, and the clearance between the squeezing roller and the cleaning roller can be constantly maintained without being influenced by a deflection of the squeezing roller due to high load placed thereon.
Preferably, the spacer is a disc provided at an end portion of the cleaning roller, and rotates integrally therewith.
Accordingly, with this simple construction, the clearance between the cylindrical outer peripheral surface of the squeezing roller and the cylindrical outer peripheral surface of the cleaning roller can be maintained.
Also, the disc may be attached on the cylindrical outer peripheral surface of the squeezing roller, and may contact the cylindrical outer peripheral surface of the bare pipe of the squeezing roller. The disc may also be fixed to a rotary shaft of the cleaning roller.
The disc may contact with the cylindrical outer peripheral surface of the bare pipe of the squeezing roller.
The disc may be fixed to a rotary shaft of the cleaning roller.
By the construction set forth above, depending upon the size of the disc as the spacer, the clearance between the cleaning roller and the squeezing roller can be adjusted.
In another preferred construction, an engaging dimension between an external diameter of the shaft of the cleaning roller and an internal diameter of a bearing is set such that the radial thickness portion of the disc defines the radial thickness portion of the disc defines the clearance between the squeezing roller and the cleaning roller and the clearance can be constantly maintained.
Accordingly, since the clearance between the squeezing roller and the cleaning roller can be constantly maintained by defining only the dimension of the thickness portion of the disc as the spacer, manufacturing of the image forming apparatus can be easily facilitated.
The image forming apparatus may further comprise a cleaning blade having a tip end thereof in contact with the outer peripheral surface of the cleaning roller for removing toner particles electrically deposited on the outer peripheral surface of the cleaning roller, and a liquid toner storage portion for storing the liquid toner defined around the tip end portion of the cleaning blade.
Accordingly, with the stored liquid toner, the toner particles stacked on the tip end portion of the cleaning blade can be removed without contact between the ends of the brush of the brush roller and the tip end portion of the cleaning blade.
The liquid toner storage portion may be adjustable so as to vary the liquid toner storage amount.
By this, the cleaning effect of the tip end portion of the cleaning blade can be adjusted.